The GenericParser is a robust C# implementation of a parser for delimited and fixed width format files. It provides a variety of features (ex. custom delimiters, text qualifiers, loading/saving configuration from XML, and many more), performant, and thoroughly tested.

Ookii.CommandLine is a powerful command line parsing library for .Net applications. It allows you to easily define a set of accepted arguments, and then parse the
command line supplied to your application for those arguments. In addition, it allows you to generate usage help from the arguments...
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The Command Line Parser Library offers to CLR applications a clean and concise API for manipulating command line arguments and related tasks. This is a fork of the original project, including most pull requests.

Cauldron.Consoles is a Cauldron.Core based parameter parser which supports grouping of parameters in execution groups. It is also supports localization and has a nice parameter table :)
Breaking changes in 3.1.x - See https://github.com/Capgemini/Cauldron for more information.

dcsoup is a .NET library for working with real-world HTML. It provides a very convenient API for extracting and manipulating data, using the best of DOM, CSS, and jquery-like methods.
This library is basically a port of jsoup, a Java HTML parser library. see also: http://jsoup.org/
API reference is...
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Turn unstructured HTML pages into structured data. The OpenScraping library can extract information from HTML pages using a JSON config file with xPath rules. It can scrape even multi-level complex objects such as tables and forum posts.